prefer-hooks-on-top.md

Suggest having hooks before any test cases (prefer-hooks-on-top)

While hooks can be setup anywhere in a test file, they are always called in a specific order, which means it can be confusing if they're intermixed with test cases.

This rule helps to ensure that hooks are always defined before test cases.

Rule details

Examples of incorrect code for this rule

/* eslint jest/prefer-hooks-on-top: "error" */

describe('foo', () => {
  beforeEach(() => {
    seedMyDatabase();
  });

  it('accepts this input', () => {
    // ...
  });

  beforeAll(() => {
    createMyDatabase();
  });

  it('returns that value', () => {
    // ...
  });

  describe('when the database has specific values', () => {
    const specificValue = '...';

    beforeEach(() => {
      seedMyDatabase(specificValue);
    });

    it('accepts that input', () => {
      // ...
    });

    it('throws an error', () => {
      // ...
    });

    afterEach(() => {
      clearLogger();
    });
    beforeEach(() => {
      mockLogger();
    });

    it('logs a message', () => {
      // ...
    });
  });

  afterAll(() => {
    removeMyDatabase();
  });
});

Examples of correct code for this rule

/* eslint jest/prefer-hooks-on-top: "error" */

describe('foo', () => {
  beforeAll(() => {
    createMyDatabase();
  });

  beforeEach(() => {
    seedMyDatabase();
  });

  afterAll(() => {
    clearMyDatabase();
  });

  it('accepts this input', () => {
    // ...
  });

  it('returns that value', () => {
    // ...
  });

  describe('when the database has specific values', () => {
    const specificValue = '...';

    beforeEach(() => {
      seedMyDatabase(specificValue);
    });

    beforeEach(() => {
      mockLogger();
    });

    afterEach(() => {
      clearLogger();
    });

    it('accepts that input', () => {
      // ...
    });

    it('throws an error', () => {
      // ...
    });

    it('logs a message', () => {
      // ...
    });
  });
});